A polymer blend (including a polymer alloy) that is produced by mixing resins which differ in polarity to modify the properties of the resins is extensively studied (see Patent Literatures 1 and 2, for example).
When the compatibility of the resins is insufficient, a deterioration in mechanical properties (e.g., impact strength) may occur, and the modification effects due to the polymer blend may not be obtained. Therefore, it is necessary to improve the compatibility of the resins using some kind of method. For example, in the case of producing a polymer alloy of a polypropylene resin and a polyamide resin, a method that utilizes a compatibilizer (e.g., anhydrous maleic acid-modified polypropylene) is proposed to improve compatibility.
Interior automotive components and exterior automotive components require high mechanical properties, and indispensably need compatibility between impact strength and rigidity (flexural modulus).
However, in the above-described polymer blends, impact strength and rigidity are in a trade-off relation. In particular, since they are in a reciprocal relation in which when impact strength is emphasized, rigidity becomes insufficient, a polymer blend that exhibits both sufficient impact strength and sufficient rigidity has not been obtained yet.
Conventionally, polylactic acid (PLA), polybutylene succinate (PBS), polytrimethylene terephthalate (PTT), polyamide 11 (PA11), and the like are known as a plant-derived resin used for a plant-derived plastic material. An alloyed plant-derived plastic material is known that is produced by blending a petroleum-derived resin (e.g., polyolefin resin or ABS) with a plant-derived resin. For example, Patent Literatures 3 and 4 describe an example of an alloyed plant-derived plastic material that utilizes PLA. Patent Literatures 5 and 6 describe an example of an alloyed plant-derived plastic material that utilizes PBS. Further, Patent Literature 7 describes an example of an alloyed plant-derived plastic material that utilizes PAH.
However, a plant-derived plastic material that utilizes PLA, PBS, or PTT has a problem in that the properties of the plant-derived resin may remain unchanged (in particular, sufficient mechanical properties may not be obtained). For example, impact strength, heat resistance, and hydrolyzability may not be sufficiently achieved when using PLA, rigidity, heat resistance, and hydrolyzability may not be sufficiently achieved when using PBS, and impact strength and hydrolyzability may not be sufficiently achieved when using PTT. Therefore, use of a plant-derived resin (plant-derived plastic material) is limited (e.g., it is difficult to apply a plant-derived resin (plant-derived plastic material) as an automotive interior material to parts (e.g., door trim or deck side trim) for which particularly high mechanical properties are required). In the case of using a plant-derived resin as a base material, it is necessary to modify the resin, and an increase in cost may occur. A thermoplastic resin composition that utilizes PA11, disclosed in Patent Literature 5 has a problem in that an ABS resin (inexpensive general-purpose plastic) that is used in combination with PA11 is expensive as compared with an olefin-based resin (e.g., polypropylene), and has insufficient solvent resistance since it is an amorphous resin.
High mechanical properties are required in automobile field including interior parts and exterior parts, and it is indispensable to achieve impact strength and rigidity (flexural modulus) in combination.
However, in the above-described polymer blends, impact strength and rigidity are in a trade-off relation. In particular, since they are in a reciprocal relation in which when impact strength is emphasized, rigidity becomes insufficient, both of impact strength and rigidity have not been fully satisfied so far.